Professional Digital Router Interview Preparation Guide

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The International Organization for Standardization (ISO) developed the Open Systems Interconnection (OSI) Reference Model to describe how information is transferred from one machine to another.

Micro segmentation is a term used with switches when each networking device has its own dedicated port on a switch.

A cooperative trade association responsible for the "Commercial Building Telecommunication Cabling Standard," also known as EIA/TIA 568, which specifies how network cables should be installed in a commercial site.

ARP, or Address Resolution Protocol can be likened to DNS for MAC Addresses. Standard DNS allows for the mapping of human-friendly URLs to IP addresses, while ARP allows for the mapping of IP addresses to MAC addresses. In this way it lets systems go from a regular domain name down to the actual piece of hardware it resides upon.

Logon scripts are, surprisingly enough, scripts that run at logon time. These are used most times to allow for the continued access to share and device mapping as well as forcing updates and configuration changes. In this way, it allows for one-step modifications if servers get changed, shares get renamed, or printers get switched out for example.

The three basic ways to authenticate someone are: something they know (password), something they have (token), and something they are (biometrics). Two-factor authentication is a combination of two of these methods, oftentimes using a password and token setup, although in some cases this can be a PIN and thumbprint.

The Encrypted File System, Microsoft's built-in file encryption utility has been around for quite some time. Files that have been encrypted in such a way can appear in Windows Explorer with a green tint as opposed to the black of normal files or blue for NTFS compressed files. Files that have been encrypted are tied to the specific user, and it can be difficult to decrypt the file without the user's assistance. On top of this, if the user loses their password it can become impossible to decrypt the files as the decryption process is tied to the user's login and password. EFS can only occur on NTFS formatted partitions, and while it is capable of encrypting entire drives it is most often reserved to individual files and folders. For larger purposes, Bitlocker is a better alternative.

A type of signal interference caused by signals transmitted on one pair of wires bleeding over into the other pairs. Crosstalk can cause network signals to degrade, eventually rendering them unviable.

Boot to LAN is most often used when you are doing a fresh install on a system. What you would do is setup a network-based installer capable of network-booting via PXE. Boot to LAN enables this by allowing a pre-boot environment to look for a DHCP server and connect to the broadcasting network installation server. Environments that have very large numbers of systems more often than not have the capability of pushing out images via the network. This reduces the amount of hands-on time that is required on each system, and keeps the installs more consistent.

Sticky ports are one of the network admin's best friends and worst headaches. They allow you to set up your network so that each port on a switch only permits one (or a number that you specify) computer to connect on that port by locking it to a particular MAC address. If any other computer plugs into that port, the port shuts down and you receive a call that they can't connect anymore. If you were the one that originally ran all the network connections then this isn't a big issue, and likewise if it is a predictable pattern then it also isn't an issue. However if you're working in a hand-me-down network where chaos is the norm then you might end up spending a while toning out exactly what they are connecting to.

RDP or Remote Desktop Protocol is the primary method by which Windows Systems can be remotely accessed for troubleshooting and is a software-driven method. KVM or Keyboard Video and Mouse on the other hand allows for the fast-switching between many different systems, but using the same keyboard, monitor and mouse for all. KVM is usually a hardware-driven system, with a junction box placed between the user and the systems in question- but there are some options that are enhanced by software. KVM also doesn't require an active network connection, so it can be very useful for using the same setup on multiple networks without having cross-talk.

While we're on the subject of Apple, Appletalk is a protocol developed by Apple to handle networking with little to no configuration (you may be sensing a pattern here). It reached its peak in the late 80s and early 90s, but there are still some devices that utilize this protocol. Most of its core technology has been moved over to Bonjour, while UPnP (Universal Plug and Play) has picked up on its ideology and moved the concept forward across many different hardware and software packages.

Routing is a process of finding a path to transfer data from source to destination.

TIA/EIA-568-B

The ability to remote into servers without having to actually be there is one of the most convenient methods of troubleshooting or running normal functions on a server- Terminal Services allow this capability for admins, but also another key function for standard users: the ability to run standard applications without having to have them installed on their local computers. In this way, all user profiles and applications can be maintained from a single location without having to worry about patch management and hardware failure on multiple systems.

Being able to ping out to a server and see if its responding is a great way to troubleshoot connectivity issues. But what if you're not able to ping ANY server? Does that mean that your entire network is down? Does it mean that your network cable needs to be replaced? Does it mean that your network card is going bad? Or could it possibly be that sunspots, magnets, aliens and the Men In Black are all conspiring against you? The answers to these questions could be very difficult, but at the very least you can rule out if your network card is going bad. 127.0.0.1 is the loopback connection on your network interface card (NIC)- pinging this address will see if it is responding. If the ping is successful, then the hardware is good. If it isn't, then you might have some maintenance in your future. 127.0.0.1 and localhost mean the same thing as far as most functions are concerned, however be careful when using them in situations like web programming as browsers can treat them very differently.

HTTPS or Secure HTTP (Not to be confused with SHTTP, which is an unrelated protocol), is HTTP's big brother. Designed to be able to be used for identity verification, HTTPS uses SSL certificates to be able to verify that the server you are connecting to is the one that it says it is. While there is some encryption capability of HTTPS, it is usually deemed not enough and further encryption methods are desired whenever possible. HTTPS traffic goes over TCP port 443.

VoIP is far better than traditional telephony but it has some drawbacks as listed below:

☛ Some VoIP services don't work during power outages and the service provider may not offer backup power.
☛ Not all VoIP services connect directly to emergency services through 9-1-1.
☛ VoIP providers may or may not offer directory assistance/white page listings.

A Firewall put simply keeps stuff from here talking to stuff over there. Firewalls exist in many different possible configurations with both hardware and software options as well as network and host varieties. Most of the general user base had their first introduction to Firewalls when Windows XP SP2 came along with Windows Firewall installed. This came with a lot of headaches, but to Microsoft's credit it did a lot of good things. Over the years it has improved a great deal and while there are still many options that go above and beyond what it does, what Windows Firewall accomplishes it does very well. Enhanced server-grade versions have been released as well, and have a great deal of customization available to the admin.

☛ A domain local group is a security or distribution group that can contain universal groups, global groups, other domain local groups from its own domain, and accounts from any domain in the forest. You can give domain local security groups rights and permissions on resources that reside only in the same domain where the domain local group is located.

☛ A global group is a group that can be used in its own domain, in member servers and in workstations of the domain, and in trusting domains. In all those locations, you can give a global group rights and permissions and the global group can become a member of local groups. However, a global group can contain user accounts that are only from its own domain.

☛ A universal group is a security or distribution group that contains users, groups, and computers from any domain in its forest as members. You can give universal security groups rights and permissions on resources in any domain in the forest. Universal groups are not supported.

SSH or Secure Shell is most well known by Linux users, but has a great deal that it can be used for. SSH is designed to create a secure tunnel between devices, whether that be systems, switches, thermostats, toasters, etc. SSH also has a unique ability to tunnel other programs through it, similar in concept to a VPN so even insecure programs or programs running across unsecure connections can be used in a secure state if configured correctly. SSH runs over TCP port 22.

Error 5 is very common when dealing with files and directories that have very specific permissions. When trying to copy elements from areas that have restricted permissions, or when trying to copy files to an area that has restricted permissions, you may get this error which basically means "Access denied". Checking out permissions, making sure that you have the appropriate permissions to both the source and destination locations, and making yourself the owner of those files can help to resolve this issue. Just remember that if you are not intended to be able to view these files to return the permissions back to normal once you are finished.

Similar to how a DNS server caches the addresses of accessed websites, a proxy server caches the contents of those websites and handles the heavy lifting of access and retrieval for users. Proxy servers can also maintain a list of blacklisted and whitelisted websites so as to prevent users from getting easily preventable infections. Depending on the intentions of the company, Proxy servers can also be used for monitoring web activity by users to make sure that sensitive information is not leaving the building. Proxy servers also exist as Web Proxy servers, allowing users to either not reveal their true access point to websites they are accessing and/or getting around region blocking.

SNMP is the "Simple Network Management Protocol". Most systems and devices on a network are able to tell when they are having issues and present them to the user through either prompts or displays directly on the device. For administrators unfortunately, it can be difficult to tell when there is a problem unless the user calls them over. On devices that have SNMP enabled however, this information can be broadcast and picked up by programs that know what to look for. In this way, reports can be run based on the current status of the network, find out what patches are current not installed, if a printer is jammed, etc. In large networks this is a requirement, but in any size network it can serve as a resource to see how the network is fairing and give a baseline of what its current health is.

The simple answer is that Multimode is cheaper but can't transmit as far. Single Mode has a smaller core (the part that handles light) than Multimode, but is better at keeping the light intact. This allows it to travel greater distances and at higher bandwidths than Multimode. The problem is that the requirements for Single Mode are very specific and as a result it usually is more expensive than Multimode. Therefore for applications, you will usually see Multimode in the datacenter with Single Mode for long-haul connections.